FIG. 1 discloses a feeder 10 being placed on a scanner 20 and the feeder 10 includes an upper guide plate 12 and two low guide plates 14, 16 located therein so as to define a passage 18 for feeding the sheets. When the feeder 10 is installed on the scanner 20, the low guide plates 14, 16 contact the glass window 22 of the scanner 20. When a document 24 is fed and pass the passage 18, the document is scanned by a scanning module set 23.
Because the low guide plate 16 has a certain thickness so that an end 17 of the low plate 16 protrudes from the glass window 22 and the document is blocked by the end 17 when it is fed.
The low guide plate 14 is located close to a surface of the glass window 22 and an end 15 of the low guide plate 14 protrudes from the glass window 22. However, the height difference between the end 15 and the glass window 22 is helpful for the feed of the document 24.
In order to resolve the problem of the jamming of the document 24, arranging the end 17 of the low guide plate 16 to be lower than the glass window 22 is a reasonable way.
FIG. 2 discloses that a first glass window 26 and a second glass window 28 are installed on the scanner 20. The first glass window 26 and the second glass window 28 are located in separate and a gap 25 is defined between the first glass window 26 and the second glass window 28. By this arrangement, the end 17 of the low guide plate 16 can be extended into the gap 25 and is located below the surface of the first glass window 26.
The two separate first glass window 26 and second glass window 28 make the volume of the scanner to be bulky and require two times of assembly for the assemblers.
FIG. 3 discloses a recess 27 is defined in the glass window 22 and a block 29 is engaged with the recess 27. The end 17 of the low guide plate 16 contacts the block 29. When the document 24 is fed, the block 29 guides the document 24 to move toward the low guide plate 16 smoothly.
The recess 27 requires two times of machining on the surface of the glass window 22 and this increases the manufacturing cost of the glass window 22. The block 29 protrudes from the glass window 22 and jams the feeding of the document 24.
Furthermore, U.S. Pat. No. 5,379,095 discloses a small piece of glass window is adhered on a large glass window so as to form a height difference in FIG. 8. The thickness of the small glass window is required to be thin so as to keep the scope of the area to be scanned in the effective focal depth, thereby causing breakage during adhering. Alternatively, the area where the small glass window is to be adhered has to be maintained in a high standard of cleanness, or the dust located between the two glass windows affects the quality of scanning.